I like to create a UISegmentedControl that looks like the scope button in UISearchBar.
You don't have direct access to the UISegmentedControl on a UISearchBar, so you will have to set the global appearance of the UISegementedControl using the UIAppearance protocol on the UISearchBar. See Customizing Appearance in the documentation for UISearchBar.
To to set a background image for example use:
[[UISearchBar appearance] setScopeBarBackgroundImage:someImage];